Unreal kind of changes the color space when outputting media via SDI Out.
The input works fine but all my monitors are showing the picture with more contrast in the dark areas so working with external live preview is not possible.
Have you had a look at the post process settings to verify that they aren’t causing the issues you seem to have? Even if you are not using a post process volume, post process effects are still being applied. You can turn off these effects in the project settings menu under rendering.